Liquid rubbers are well established and have uses which include more particularly that of increasing toughness. Through the use of chemically reactive groups, such as hydroxyl, carboxyl, vinyl or amino groups, such liquid rubbers can be incorporated chemically into the matrix. Thus, for example, there have long been reactive liquid rubbers in existence that have a butadiene/acrylonitrile polymer backbone, these rubbers being offered by B.F. Goodrich, or Noveon, under the trade name Hycar®.
Known amino-terminated liquid rubbers of this kind, such as those available commercially under the Hycar® ATBN product series, are used more particularly for epoxy resins, as a curing component, for increasing the impact toughness. These known amino-terminated liquid rubbers, however, have amino groups, which owing to the structure are readily accessible and therefore highly reactive, and occasionally have tertiary amino groups. If amino-terminated liquid rubbers of this kind are used for preparing prepolymers or compounds that contain isocyanate groups or epoxide groups, unwanted crosslinking reactions mean that storage-stable compositions are impossible.